Less than a week after the discovery of a sophisticated drug tunnel operating beneath the Arizona-Mexico border, two more illicit underground passageways have been found under construction on the San Diego-Tijuana border, authorities announced Thursday.

Otay Drug Tunnel

One entrance was discovered late Wednesday by Mexican soldiers east of A.L. Rodríguez International Airport, leading from a building that apparently housed a recycling business. The entrance was located beneath the sink of a restroom in the structure.

A statement Thursday from Baja California’s Second Military Zone said that the incomplete tunnel extends 150 meters--nearly 500 feet--and has electricity and ventilation. The entrance plunges down 33 feet to the tunnel, which is over three feet wide and five-and-a-half feet high, according to the military’s statement.

The tunnel had been under investigation by members of the San Diego Tunnel Task Force, which includes agents from U.S. Immigration and Customs Enforcement, the U.S. Drug Enforcement Administration, the Border Patrol and U.S. Customs and Border Protection. No arrests were reported.

On Thursday night, the Mexican military reported finding a second incomplete tunnel following the discovery of 40 tons of marijuana in an area known as Colonia Granjas Familiares del Matamoros. The tunnel extended more than 1,100 feet toward the border, authorities said.

The entrances were found less than a week after the discovery Saturday of a suspected drug tunnel operating on the Arizona border south of Yuma. According to a statement released Thursday by the DEA, that tunnel measured 240 yards and linked an empty business in San Luis, Ariz., with an ice plant in San Luis Río Colorado, Mexico.

/ DEA

Photograph of the tunnel found Saturday on the Arizona border.

Photograph of the tunnel found Saturday on the Arizona border. (/ DEA)

The statement described the passageway as “the only completed and fully operational smuggling tunnel ever uncovered in the Yuma, Arizona area.”

The tunnel was equipped with lighting and a ventilation system, according to the DEA’s statement. Agents found the Arizona entrance hidden beneath a large water tank inside a storage room, leading down 55 feet, according to the statement. The tunnel’s walls are more than six feet high, it said, and are reinforced every few feet with with support beams; plywood covers the walls, ceiling and floor.

The building had been under surveillance since DEA agents first noticed suspicious activity in January. A break in the case came last Friday, when a traffic stop on Interstate-95 by the Arizona Department of Public Safety led to the discovery of methamphetamine inside a Ford F-150; the trail led back to the building, the DEA said.

Three suspects were in custody Thursday, the DEA reported.

Over the past 10 years, 89 cross-border tunnels have been found along the Arizona border, and 50 others have been discovered along the California border, according to the DEA. As increased enforcement has made it harder for smugglers, criminal groups build the illicit tunnels to move drugs and people across the border.